Field of the Invention
The invention relates generally to the field of manufacturing large mill cylinders. More specifically, the invention relates to a method for manufacturing large mill cylinders, wherein the mill cylinder is composed of a plurality of cylinder sections which are welded to one another.
Description of the Related Art
Mill cylinders comprising a plurality of cylindrical sections welded to one another may display diameters of 3 to 12 m and more and are employed for ball mills, autogenous mills, and semi-autogenous mills, for example. These mills typically are circumferentially mounted, wherein raceways which interact with correspondingly configured friction bearings are provided on the end regions of the mill cylinder, as shown for example in German Patent Application No. DE 89 13 313 U1. It is of decisive significance in the case of this type of mounting that the individual cylinder sections are exactly aligned in relation to the common mill axis and also the end edges to be welded to one another are aligned so as to be concentric and orthogonal in relation to the raceway face.
On account of the large dimensions, the complete mill cylinder cannot be shipped any more. Therefore, it is typical that the individual cylinder sections are shipped to the construction site having end edges which are prepared for welding and are welded to one another only on site. To this end, the applicant has developed what is referred to as the Polweld® method.
Since ever larger mill cylinders have been built in recent times, shipping of the individual cylinder sections to the construction site is also associated with enormous costs. Here, not only the shipping costs but also any applicable import duties on semi-finished products have to be taken into account. Therefore, it has been proposed in DE 89 13 313 U1 to divide the mill cylinders and the raceways in the longitudinal direction and to interconnect the component parts using flanges.
German Patent Application No. DE 12 81 810 A1 discloses a centering device for large cylinder sections to be welded to one another, in particular in the case of tube mills.